Metalloproteinases represent a super family of proteinases (enzymes), whose numbers have increased dramatically in recent years. Based on structural and functional considerations, these enzymes have been classified into families and subfamilies N. M. Hooper, FEBS letters 354, 1-6 (1994). Examples of metalloproteinases include the matrix metalloproteinases (MMPs), which is a family of zinc containing endopeptidases, such as the collagens (MMP-1, MMP-8, MMP-13, MMP-18), the gelatinases (MMP-2, MMP-9), the stromelysins (MMP-3, MMP-10, MMP-11), matrilysin (MMP-7, MMP-26), metalloelastase (MMP-12) enamelysin (MMP-20), the MT-MMPs (MMP-14, MMP-15, MMP-16, MMP-17, MMP-24, MMP-25).
The MMPs is a family of zinc containing endopeptidases which are capable of cleaving large biomolecules like the collagens, proteoglycans and fibronectins, a process necessary for the growth and remodelling of tissues such as embryonic development and bone formation under normal physiological conditions. Expression is upregulated by pro-inflammatory cytokines and/or growth factors. The MMP's are secreted as inactive zymogens which, upon activation, are subject to control by endogenous inhibitors, for example, tissue inhibitor of metalloproteinases (TIMP) and α-macroglobulin. Chapman, K. T. et al., J. Med. Chem. 36, 4293-4301 (1993); Beckett, R. P. et al., DDT 1, 16-26 (1996). The characterizing feature of diseases involving the enzymes appears to be a stoichiometric imbalance between active enzymes and endogenous inhibitors, leading to excessive tissue disruption, and often degradation. McCachren, S. S., Arthritis Rheum. 34, 1085-1093 (1991).
Over-expression and activation of MMPs have been linked with a wide range of diseases such as cancer, tumour metastasis, rheumatoid arthritis, osteoarthritis, chronic inflammatory disorders such as emphysema, cardiovascular disorders such as atherosclerosis, corneal ulceration, dental diseases such as gingivitis and periodontal disease, and neurological disorders such as multiple sclerosis. Chirivi, R. G. S. et al., Int. J. Cancer, 58, 460-464 (1994); Zucker, S., Cancer Research, 53, 140-144 (1993). In addition, a recent study indicates that MMP-12 is required for the development of smoking-induced emphysema in mice. Science, 277, 2002 (1997). MMP-12, also known as macrophage elastase or metalloelastase, was initially cloned in the mouse by Shapiro et al., J. Biological Chemistry, 267, 4664 (1992) and in man by the same group in 1995. Structurally, the proMMP-12 consists of a pro-domain, a catalytic domain containing the zinc binding site and a C-terminal hemopexin-like domain. Recombinant human MMP-12 can be activated by autocatalysis as described below and reviewed by Shapiro et al “Macrophage Elastase” in Handbook of Proteolytic Enzymes 2004 (Eds A J Barrett et al) pp 540-544 Academic Press, San Diego.
MMP-12 is preferentially expressed in activated macrophages and its expression in monocytes can be induced by cytokines such as GM-CSF and CD-40 signalling. In addition to elastin, MMP-12 can degrade a broad spectrum of substrates, including type IV collagen, fibronectin, laminin, vitronectin, proteoglycans, chondroitin sulphate, myelin basic protein, alpha-one chymotrypsin and plasminogen. It can also activate MMP-2 and MMP-3. MMP-12 is required for macrophage mediated proteolysis and matrix invasion in mice. MMP-12 is proposed to have a direct role in the pathogenesis of aortic aneurisms and in the development of pulmonary emphysema that results from chronic inhalation of cigarette smoke, wood smoke and urban smogs.
MMP-12 has been shown to be secreted from alveolar macrophages from smokers Shapiro et al., J. Biological Chemistry, 268, 23824, (1993) as well as in foam cells in atherosclerotic lesions Matsumoto et al., Am. J. Pathol, 153, 109, (1998). A mouse model of COPD is based on challenge of mice with cigarette smoke for six months, two cigarettes a day six days a week. Wildtype mice developed pulmonary emphysema after this treatment. When MMP-12 knock-out mice were tested in this model they developed no significant emphysema, strongly indicating that MMP-12 is a key enzyme in the COPD pathogenesis. The role of MMPs such as MMP-12 in COPD (emphysema and bronchitis) is discussed in Anderson and Shinagawa, Current Opinion in Anti-inflammatory and Immunomodulatory Investigational Drugs: 29-38 (1999). It was recently discovered that smoking increases macrophage infiltration and macrophage-derived MMP-12 expression in human carotid artery plaques Kangavari (Matetzky S, Fishbein M C et al., Circulation 102, (18), 36-39 Suppl. S, Oct. 31, (2000).
Apart from the role of these potentially very destructive enzymes in pathology, the MMPs play an essential role in cell regrowth and turnover in healthy tissue. Broad spectrum inhibition of the MMPs in the clinical setting results in musculoskeletal stiffness and pain. H. S. Rasmussen and P. P. McCann, Pharmacol. Ther., 75, 69-75 (1997). This side effect and others associated with broad spectrum inhibition may be enhanced in chronic administration. Thus, it would be advantageous to provide selective MMP inhibitors.
The inhibition of such MMP-12 activities is considered to contribute to the improvement and prevention of the above discussed diseases caused by or related to the activity of MMP-12. Therefore, the development of MMP-12 inhibitors has been desired.
A number of metalloproteinase inhibitors are known and described in the literature, (see for example the reviews of MMP inhibitors by Beckett R. P. and Whittaker M., 1998, Exp. Opin. Ther. Patents, 8 (3):259-282.
Whittaker M. et al, 1999, Chemical Reviews 99 (9): 2735-2776) review a wide range of known MMP inhibitor compounds. They state that an effective MMP inhibitor requires a zinc binding group, i.e. a functional group capable of chelating the active site zinc(II) ion, at least one functional group which provides a hydrogen bond interaction with the enzyme backbone, and one or more side chain which undergo effective van der Waals interactions with the enzyme subsites. Zinc binding groups in known MMP inhibitors include carboxylic acid groups, hydroxamic acid groups, sulfhydryl groups or mercapto groups.
Despite the potent affinity of hydroxamic acid as zinc coordinator, hydroxamic acid inhibitors demonstrate a considerable degree of specificity within the MMP family: a potent inhibitor of one member of the MMP family, may have only minimal potency against another MMP family member. This exhibited specificity typically relies on the identity of the other parts of the inhibitors, e.g. the P1, P2, P3 and P4 units. Without in any way wishing to be bound by theory, or the ascription of tentative binding modes for specific variables, the notional concepts P1, P2, P3 and P4 are used herein for convenience only and have substantially their conventional meanings, as illustrated by Schechter & Berger, (1976) Biochem Biophys Res Comm 27 157-162, and denote those portions of the inhibitor believed to fill the S1, S2, S3 and S4 subsites respectively of the enzyme, where S1 is adjacent the cleavage site and S4 remote from the cleavage site.
There are several patents which disclose hydroxamate-based inhibitors of metalloproteases or analogous enzymes.
WO02/028829 describes inhibitors of peptide deformylase (PDF) useful for example in the development of new antibacterial drugs. PDF is a bacterial enzyme which shares several structural features in common with zinc metalloproteases. PDF does not cleave a peptide bond, but rather cleaves off the N-formyl group from the terminal N-formyl methionine which characterises the nascent bacterial polypeptide chain. Despite the fact that the compounds of WO02/028829 comprise a hydroxamic acid group the SAR (structure activity relationship) exhibited by these inhibitors is not helpful to the design of specific inhibitors of the endopeptidase MMP-12. An endopeptidase cleaves within a peptide chain, and therefore the protease typically recognises a number of amino acid residues around the intended cleavage site. In contrast PDF is intended to cleave a terminal group on the first amino acid of bacterial proteins of very different sequence. Accordingly the selectivity of PDF is predicated on recognition of the N-formyl.methionine terminal residue rather than the identity of the adjacent amino acids.
US 3003/0134827 discloses compounds having a hydroxyacetamide moiety linked to a broad range of cyclic amides as inhibitors of MMPs in particular MMP-3, aggrecanase and TNF-α-converting enzyme (TACE). Although hydantoin is postulated as one of many such cyclic amides, US 2003/0134827 discloses no concrete examples of compounds within the scope of this invention. As demonstrated in the following biological examples, the compounds of the invention achieve potent MMP-12 inhibition while at the same time being highly selective against the enzymes addressed in US 2003/0134827.
U.S. Pat. No. 6,462,063 discloses substituted hydantoin hydroxamates capable of inhibiting C-proteinase. In contrast to the compounds of the invention defined below, the compounds of U.S. Pat. No. 6,462,063 have a hydroxamic acid linked to a carbon atom of the hydantoin ring via a chain comprising, apart from the acid function, at least three atoms. By varying the length of the hydroxamic acid carrying chain and the substitution pattern of the hydantoin ring, the binding properties to the enzyme and hence the specificity of the inhibitor will be altered. The hydroxamate function of U.S. Pat. No. 6,462,063 is thus sitting on the other side of the hydantoin ring compared to the compounds of the invention defined below and is also disposed further out from the hydantoin. These kind of structural variations between the class of compounds disclosed in U.S. Pat. No. 6,462,063 and inhibitors based on hydantoin hydroxamates wherein the hydroxamic acid is linked to a nitrogen atom of a hydantoin group via a one atom chain, will render the SAR exhibited by the compounds of U.S. Pat. No. 6,462,063 of no relevance to the design of specific inhibitors of MMP-12
WO02/074750 discloses a new class of compounds that act as MMP inhibitors wherein the zinc binding group of the inhibitor is constituted of a five membered ring structure such as a hydantoin group. The zinc binding ring structure is attached to one or more functional groups or side chains which are disposed at an appropriate angle and distance to recognise the characteristic sequence around the appropriate MMP12 cleavage site. The mode of binding to the enzyme of this class of zinc-binding inhibitors will thus differ substantially from that of compounds having other zinc binding groups, such as hydroxamic acid adjacent a hydantoin core, in that coordination of the hydroxamate zinc binding group will displace the hydantoin away from the structural zinc. Any further substituents opposed from the hydroxamate will also be displaced away from the structural zinc and will interact with other parts of the enzyme. Due to this different binding mode of the compounds disclosed in WO02/074750 compared to hydantoin hydroxamates, the SAR found for the P1, P2, P3 and P4 units of the compounds of WO02/074750 is not relevant to the design of new MMP inhibitors based on a hydantoin hydroxamate scaffold.
Similarly, US 2005/0171096 discloses hydantoin derivatives alleged to be inhibitors of matrix metalloproteinases and TACE although no guidance as to the specificity of the inhibitors is given. The compounds of US 2005/0171096 do not bear a hydroxamic acid or conventional zinc-binding group. This suggests that that the hydantoin is the zinc binding group and hence the SAR exhibited by the P1, P2 and P3 units of these compounds is different from that of an inhibitor based on a hydantoin substituted with a hydroxamic acid carrying side chain.
As foreshadowed above, we have now discovered a particular configuration of hydroxamic hydantoins that are inhibitors of metalloproteinases and are of particular interest in selectively inhibiting MMPs such as MMP-12 and have desirable activity profiles. The compounds of this invention have beneficial potency, selectivity and/or pharmacokinetic properties.